JPH01215495A - Flux cored wire for self-shielded arc welding - Google Patents

Abstract

PURPOSE:To improve the porosity resistance of a wire and the stability of an arc by adding an Li at specified wt.% in the form of an Al-Li alloy into a flux and regulating the moisture amt. per wire total weight at specified rate. CONSTITUTION:Li is added at 1-50wt.% into a flux in the form of an Li-A alloy(Li contg. amt. in the alloy is 0.1-50at%), moreover the moisture contg. amt. per wire total weight is regulated in 100-4000ppm. The nitrogen amt. in a welding metal is remarkably reduced due to the Li contg. amt. in the Al-Li and the Li amt. in the flux being adequately regulated, and the Al-Si metal powder can exist stably in the atm. The rust generation of the wire itself is prevented because the moisture amt. in the flux is regulated. The porosity resistance of the wire is thus improved and the arc is stably maintained.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a flux-cored wire for arc welding, and more particularly to a flux-cored wire for self-shielded arc welding that has good porosity resistance against pits, blowholes, etc. (Prior Art and Problems to be Solved) Conventionally, a method of using metal LL as a denitrifying agent has been proposed as one of the flux-cored wires for self-shielded arc welding (see US Pat. No. 3,691,340). ). However, since the metal L1 is very active, it is difficult to allow it to exist stably in the atmosphere for a long period of time, and the above method is considered impractical. Therefore, there is a method of adding Li to flux in the form of a Li compound such as carbonate, oxide, fluoride, or a composite compound containing these, and reducing the Li compound with a reducing agent using arc heat to obtain elemental Li. For example, in JP-A-48-4347 and JP-A-48-8627, ferrates, silicates, manganates, and aluminates are used as Li compounds. However, as is clear from the fact that the industrial method for producing Li is by molten salt electrolysis, Li is an element that is extremely difficult to reduce, so the above method results in insufficient denitrification and This often resulted in pits and blowholes. The present invention was made to solve the problems of the prior art described above, and suppresses the LL gold metal reactivity so that the wire performance does not change over a long period of time. Another object of the present invention is to provide a flux-cored wire for self-shielded arc welding that has excellent porosity resistance. (Means for Solving the Problems) In order to achieve the above object, the present inventors initially made full use of various coating methods and surface treatment techniques such as microencapsulation in order to suppress LL gold metal reactivity. However, by either method, it has been impossible to stably maintain metallic Li in the atmosphere for a long period of time. Therefore, the concentration of metallic Li is diluted. Namely. We have begun investigating the possibility of suppressing the reactivity of metal Li by alloying it. First, from the phase diagram, the element that metal Li can dissolve is /l
, Ca, Cu%Mg, Na, Sn, Zn, Ni,
Since Si and Go are considered, metal L is added to these metal elements.
Various Li-containing metal powders were produced by melting i. When various physical properties such as density, oxidation resistance, and moisture absorption were investigated for the obtained metal powder, it was found that AQ, Mg-based Li-containing metal powder is relatively promising as a Li source. Next, in consideration of safety in handling metal powder (during storage and wire manufacturing), a Hartmann type metal dust explosion test was conducted. As a result, it was found that AJ-Li based alloy is safer than Mg-Li based metal powder as Li-containing metal powder. Based on the above investigation results, we have further conducted research on the pore resistance when the AQ-Li alloy is contained in flux, and have hereby accomplished the present invention. That is, the flux-cored wire for self-shielded arc welding according to the present invention includes LL in the form of an AQ-Li alloy (however, the Li content in the alloy is 0.1 to 50 at%) in a flux of 1 to 50 Vt. %, and the moisture content per total weight of the wire is 100 to 4000 pp. The present invention will be explained in more detail below. In the present invention, AQ-
The main feature is that it is made of a Li-based alloy. The amount of AQ-Li added to the flux is determined by the arc stability (
arc flapping, arc spread, arc strength, etc.)
Judging from slag cover, amount of fume generation, bead shape, amount of nitrogen in the weld metal, etc., the range of 1 to 50 wt% is preferable.++ If it is less than 1 wt%, the effect of reducing the amount of nitrogen in the weld metal by AQ-Li is low. If it exceeds 35vt%, the arc stability will deteriorate a little and the amount of nitrogen in the weld metal will tend to increase slightly, but if it exceeds 50vt%, the shielding effect by Ll will become excessive, so The amount of fume generated becomes extremely large, which is undesirable. Therefore, the amount of He0-Li in the flux is set in the range of 1 to 50 wt%. In addition, if the amount of nitrogen in the weld metal is considered, it is more preferably 5 to 35 vt%. Here, the amount of metallic Li added in the flux can be determined by the following simple method. That is, as shown in Fig. 1, a quartz tube 2 is inserted into an electric furnace 1, and an ammonia measuring device is used that introduces N8 gas into the quartz tube via distilled water 3. For example, a flux-cored wire 4 containing a -Li alloy is heated under a humid nitrogen stream. When heated to 400°C, the metal Li in the AQ-Li alloy
reacts with nitrogen to produce Li3N. The generated Li,
Since N is very unstable, it reacts with water to form NH3 (ammonia). By absorbing this NH in distilled water and measuring the generated NH, it is possible to determine the amount of metallic Li added in the flux. In this case, if the AQ-Li alloy content in the flux is 1 to 50 vt%, NH per 100 g of wire corresponds to 0.005 to 1 g. Even in the case of Li-based alloys other than AQ-Li alloys, the amount of Li added in the flux can be determined from the determined amount of NH in the same manner. Therefore, the flag °
This simple method can be used when adjusting the speed. An-Li alloys include AQ-Li and others. In addition, the three components are Fe, Zr, Cu, Si,
Addition of Mg, Ca, ZnlMn, etc. singly or in combination (
AQ-Li'i alloy (see Japanese Patent Application No. 62-202677) containing several ppm to several at%) may also be used, and the component system is not particularly limited.According to the experimental research by the present inventors, No significant effect on denitrification was observed, and lvt%
Addition of the following trace amounts also has the effect of increasing the safety (resistance to metal dust explosion) of AQ-Li alloy powder. Such AΩ-Li alloys are manufactured by appropriate methods such as REP method, gas atomization method, mechanical pulverization method, etc.
From the viewpoint of preventing segregation during flux mixing and metal dust explosion, the particle size is desirably 45 μm or more and 500 μm or less. Particularly, if the particle size is 45 μm or more, metal dust explosion will not occur. The Li content (concentration) in the A11-Li-based alloy needs to be an appropriate amount. In this regard, the present inventors produced AQ-Li alloy powders with various Li concentrations, used them to prototype flux-cored wires for self-shielded arcs, and investigated the amount of nitrogen in the weld metal. -Li in Li
It has been found that when the content is 0.1 at% or more, the amount of nitrogen in the weld metal is significantly reduced and the porosity resistance of the wire is improved. When the Li content is gradually increased, the amount of nitrogen in the weld metal gradually decreases as the Li content increases, but this tendency is not remarkable.
The fi-Li metal powder no longer exists stably in the atmosphere. Therefore, the Li concentration is preferably in the range of 0.1 to 50 at%, and more preferably 3 to 20 at%, the denitrification effect is significant. Next, the moisture content of the flux-cored wire in the present invention will be explained. In order to maintain the Afi-Li alloy powder in a stable state for a long period of time in the wire, it is necessary to keep the wire moisture content above a certain value. In other words, A11-Li alloy powder is unstable because highly active metal Li is exposed on the surface of the metal powder, so it is necessary to change the metal Li into a stable form in advance. For example, A(1-Li alloy powder can be maintained in a stable state for a long period of time. Specifically,
A preferred method is to react the metal Li exposed on the surface of the AQ-Li alloy powder with carbon dioxide (Cox) in the air and coat the AQ-Li alloy powder with Li and Co. For this purpose, it is necessary for the metal Li to become a hydroxide and to easily absorb carbon dioxide gas, and it is advisable to increase the moisture content of the flux-cored wire. The inventors of the present invention forced the flux to absorb moisture and investigated various amounts of fluff moisture, and found that if the moisture content per total weight of the wire is 1100 pp or more, the AQ-Li alloy powder will remain in the wire for a long period of time. It was found that the condition is stable and the wire performance can be maintained constant for a long period of time as well. However, if the moisture content per total wire weight exceeds 4000 ppm. As a matter of course, it was observed that the wire itself became easily rusted, and the wire feedability, current conductivity, arc stability, etc. tended to deteriorate. Therefore, the moisture content per total wire weight is 100 to 4
Regulated within the range of 000ppm. Note that the amount of water per total weight of the wire herein refers to the amount of water extracted in 02 atmosphere at 750° C. and determined by the Karl Fischer method. Note that in the present invention, the material of the hoop, the dimensions of the wire,
Needless to say, there are no particular restrictions on the cross-sectional shape, flux rate, applicable welding material, etc. (Example) Next, an example of the present invention will be shown. A11-Li alloys with various Li concentrations shown in Table 1 were produced as prototypes. The obtained Ajl-Li alloy powder was appropriately mixed with 100 parts by weight of a mixed flux having the flux composition shown in Table 2 to prepare a filling flux for self-shielded arc welding. At this time, the moisture content per total wire weight was controlled by changing the moisture content of the raw material flux. Specifically, we may mix the same raw materials with different moisture content (the moisture content may vary greatly depending on the production area or refining process), or we may use hydrated minerals that do not affect welding workability. It was added separately to the composition shown in Table 2. A hoop material having the chemical composition shown in Table 3 was formed into a pipe shape and filled with the thus obtained filling flux at a flux filling rate of 14% to produce a flux-cored wire by a conventional method. Type of AQ-Li alloy used, weighed amount of mixed AQ-
Li addition amount ((A! - parts by weight of Li-based alloy) + (100
+AJ-Li based alloy weight part) x 100) and wire water content are as shown in Table 5. Next, using these flux-cored wires (wire diameter 1.2 mark 1 mφ), as shown in Figure 2, the thickness is 20 μm.
Fillet welded joints of 12 m thick and 500 mm long steel plates having a zinc primer of Table 5 also shows the results of investigations regarding pore resistance, fume content, and arc stability. The porosity resistance was evaluated based on the presence or absence of pits on the surface of the 2nd pass (FIG. 2), with a 0 mark indicating no pits and an x mark indicating pits present. The welding conditions in this case are 28
0AX30cpm. The amount of hume was measured according to JIS Z3930, and evaluated by marking 0 if the amount of hume generated was 1500 mg/min or less, and marking x if it was more than 1500 mg/min. The welding conditions in this case are 280AX30cp. Arc stability is determined by investigating the arc length during welding (downward bead-on-plate) using high-speed video. If the arc length fluctuation is within twice the wire diameter, it is marked 0, and if it is more than twice the wire diameter, it is marked 0. It was evaluated by marking it with an x. As is clear from Table 5, Li in the AQ-Li alloy
In test NQI where the concentration is 0.1 at% or more, and tests where the Li concentration is 0.1 at% or more but the AQ-Li alloy addition amount is lvt% or less, in 3 and 5.12, Li
Porosity resistance deteriorated due to insufficient shielding. In addition, in tests & 8.14 in which the amount of AQ-Li alloy added exceeds 50%It%, the shielding effect of Li becomes excessive, and the amount of fume generated is extremely large. It is difficult to weld. In the test @&9.17 where the moisture content per total wire weight was less than 1100 pp+, the porosity resistance and arc stability deteriorated due to the instability of the AQ-Li alloy. This is considered to be because the Afi-Li alloy is in a state where it is very easily oxidized and is oxidized before being exposed to the arc atmosphere, reducing the shielding effect of Li. In addition, in test &15 where the moisture content per total weight of the wire exceeded 4000pp-, the high moisture content caused the wire to rust easily, causing rust to occur on the inner and outer surfaces of the wire, resulting in poor conduction and significantly deteriorating the stability of the arc. did. In contrast, the test rods of the present invention examples 2.4.6 to 7.10
-11, 13, 16.18 have excellent porosity resistance, a small amount of fume generation, and excellent arc stability.

[Left below]

AQ-L shown in Table 1 in the same manner as in Example 1
The i-based alloy was appropriately mixed with 100 parts by weight of a mixed flux having the flux composition shown in Table 6 to prepare a filling flux for self-shielded arc welding. Type of AQ-Li alloy used - AM mixed by weighing -
The amount of Li-based alloy added and the amount of water in the wire are as shown in Table 9. The moisture content of the wire was adjusted by changing the moisture content of the raw material flux to be filled. A hoop material having the chemical composition shown in Table 7 was formed into a pipe shape and filled with the obtained filling flux at a flux filling rate of 13% to produce a flux-cored wire by a conventional method. Using these manufactured flux-cored wires for self-shielded arc welding, welding was performed under the welding conditions shown in Table 8, and the porosity resistance, fume generation amount, and arc of the wire were determined in the same manner as in Example 1. Stability was investigated. The results are also listed in Table 9. As is clear from Table 9, Li in the AQ-Li alloy
The concentration is O, lat% non-vortex test &1, Li concentration is 0
．． 1at% or more, but the AM-Li alloy addition amount is 1w
In Test &3 with less than t%, poor pore resistance was obtained due to insufficient shielding by Li. In addition, in tests in which the amount of AQ-Li alloy added exceeds 50vt%, the shielding effect of Li becomes excessive and the amount of fume generated is extremely large. Welding is difficult. In Test &11 in which the water content per total weight of the wire was less than 1100 pp, the arc was likely to become unstable due to the instability of the Affi-Li alloy, and the porosity resistance deteriorated. In addition, the moisture content per total wire weight is 4000PP11
In the test NcilO, the wire was easily rusted as in Example 1, and rust occurred on the inner and outer surfaces of the wire, resulting in poor conduction, the arc was likely to become unstable, and the porosity resistance was deteriorated. On the other hand, in contrast to these, the test of the present invention example &2.4°6~9
All of them have excellent pore resistance, little fume generation, and excellent arc stability.

[Left below]

(Effects of the Invention) As detailed above, according to the present invention, a flux-cored wire for self-shielded arc welding is produced by adding a specific amount of Li to the flux in the form of an Al-Li alloy with an appropriate Li concentration, and Since the amount of water per total weight of the wire is regulated, it is possible to provide a wire with excellent porosity resistance, no change in wire performance over a long period of time, and excellent workability.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an ammonia measuring device for determining the amount of AΩ-Li alloy added in a flux-cored wire, and FIG. 2 is a diagram illustrating a welding method used in an example. 1... Electric furnace, 2... Quartz tube, 3... Distilled water, 4
...Sample (flux-cored wire), 5...Power supply. Patent applicant Hisashi Nakamura, patent attorney representing Kobe Steel, Ltd. Figure 1 Figure 2

Claims (1)

[Claims] (1) Li is replaced with an Al-Li alloy (however, Li in the alloy
1 in the flux in the form of 0.1 to 50 at%).
A flux-cored wire for self-shielded arc welding, characterized in that a flux-cored wire is added with a moisture content of 100 to 4000 ppm based on the total weight of the wire.